8 research outputs found
The ABC130 barrel module prototyping programme for the ATLAS strip tracker
For the Phase-II Upgrade of the ATLAS Detector, its Inner Detector,
consisting of silicon pixel, silicon strip and transition radiation
sub-detectors, will be replaced with an all new 100 % silicon tracker, composed
of a pixel tracker at inner radii and a strip tracker at outer radii. The
future ATLAS strip tracker will include 11,000 silicon sensor modules in the
central region (barrel) and 7,000 modules in the forward region (end-caps),
which are foreseen to be constructed over a period of 3.5 years. The
construction of each module consists of a series of assembly and quality
control steps, which were engineered to be identical for all production sites.
In order to develop the tooling and procedures for assembly and testing of
these modules, two series of major prototyping programs were conducted: an
early program using readout chips designed using a 250 nm fabrication process
(ABCN-25) and a subsequent program using a follow-up chip set made using 130 nm
processing (ABC130 and HCC130 chips). This second generation of readout chips
was used for an extensive prototyping program that produced around 100
barrel-type modules and contributed significantly to the development of the
final module layout. This paper gives an overview of the components used in
ABC130 barrel modules, their assembly procedure and findings resulting from
their tests.Comment: 82 pages, 66 figure
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Direct Charm Reconstruction in Association with W Bosons at √s = 13 TeV in the ATLAS Detector
The production of a W boson in association with a single charm quark is studied using140 fb−1 of √s = 13 TeV proton–proton collision data collected with the ATLAS detector at
the Large Hadron Collider. The charm quark is tagged by the presence of a charmed hadron,
reconstructed with a secondary-vertex fit. The W boson is reconstructed from the decay to
either an electron or a muon and the missing transverse momentum present in the event.
The W + D(∗) process is sensitive to the strange quark PDF, and can be combined with
other measurements to improve uncertainties and central values of global PDF fits. Charmed
mesons are reconstructed in the decay channels D+ → K−π+π+, D∗+ → D0π+ → (K−π+)π+,
D+ → φπ → (KK)π, and Ds → φπ → (KK)π and the charge conjugate decays in the fiducial
regions where pT(e, μ) > 30 GeV , |η(e, μ)| < 2.5, pT(D(∗)) > 8 GeV , and |η(D(∗))| < 2.2.
The integrated and normalized differential cross-sections as a function of the pseudorapidity
of the lepton from the W boson decay, and of the transverse momentum of the charmed
hadron, are extracted for the D+ → Kππ and D∗ → D0π → Kππ decay modes. The
total fiducial cross section is measured for the Ds → φπ → (KK)π and D+ → φπ →
(KK)Ï€ decay modes. All observables are extracted from the data using a profile likelihood
fit. The measured total fiducial cross-sections for the D+ → Kππ and D∗ → D0π →
Kππ modes are σ(OS−SS, fid) (W −+D+) = 50.2 ± 0.2 (stat.) +2.4−2.3 (syst.) pb, σ (OS−SS, fid) (W ++D−) =
48.5 ± 0.2 (stat.) +2.3−2.2 (syst.) pb, σ(OS−SS, fid) (W −+D∗+) = 51.1 ± 0.4 (stat.) +1.9−1.8 (syst.) pb, and
σ(OS−SS, fid) (W ++D∗−) = 50.0 ± 0.4 (stat.) +1.9−1.8 (syst.) pb. These differential and total cross section
results are compared with the predictions of next-to-leading-order quantum chromodynamics
calculations performed using state-of-the-art parton distribution functions. Additionally, the
ratio of charm to anti-charm production cross-sections is studied to probe the s- Ì„s quark
asymmetry. The ratio is found to be Rc = 0.971 ± 0.006 (stat.) ± 0.011 (syst.). The ratio
and cross-section measurements are consistent with the predictions obtained with parton
distribution function sets that have a symmetric s- Ì„s sea, indicating that any s- Ì„s asymmetry in
the Bjorken-x region relevant for this measurement is small. For the Ds → φπ → (KK)π and
D+ → φπ → (KK)π analysis, the observables that are measured are the inclusive cross section
in both charges for the W +Ds process, the ratio of the cross sections with respect to the charge,
and the ratio of the Ds to the D+ process. The measured values are σ(OS−SS, fid) (W −+D+s ) =17.8±0.4 (stat.) +1.8−1.6 (syst.) pb, σ(OS−SS, fid) (W ++D−s ) = 15.8±0.4 (stat.) +1.5−1.4 (syst.) pb, Rc (Ds) =0.885 ± 0.029 (stat.)+0.059−0.057 (syst.), and R(D+/Ds) = 2.93 ± 0.06(stat.) ± 0.24 (sys.). These result are consistent with the differential W + D+ analysis within 1.5 standard deviations, and are at a lower precision due to lower data and MC simulation statistics and increased systematic
uncertainties related to background modeling
Michigan REU Summer Student Program
Development of an augmented reality mobile application for the ALICE detecto
The Heavy Flavor Production Fraction Reweighting Procedure in ATLAS
The rates at which b- and c-quarks hadronize into different hadron species (i.e. the HF production fractions) may vary among MC Shower simulations such as Pythia, Sherpa, and Herwig. Furthermore, the flavor tagging efficiencies in ATLAS have been found to depend on the hadron species inside a jet. For example, flavor tagging efficiency for c-jets is the largest for D+ mesons and the lowest for charm baryons. Because of this, flavor tagging efficiency in MC depends on the MC shower software and needs to be corrected on an individual basis. The ATLAS Collaboration developed a method of reweighting the HF production fractions to a common world average, which largely eliminates the difference in the flavor tagging efficiency between different MC samples. Moreover, the experimental uncertainties in the HF production fractions (typically 2-3% relative uncertainty) can also be applied with the same reweighting procedure which gives rise to a common way of estimating these systematic uncertainties in ATLAS
The ABC130 barrel module prototyping programme for the ATLAS strip tracker
For the Phase-II Upgrade of the ATLAS Detector [1], its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100% silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-250) [2,2] and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests